Electronic nonadiabatic interactions and ultrafast internal conversionin phenylacetylene radical cation

摘要

Quantum chemistry and dynamics of the ground X~2B_1and low-lying excited A~2A_2, B~andC~2B_1 electronic states of phenylacetylene radical cation are examined here in striving to understandits photostability, long-lived excited electronic states, and resolved (<10 meV) vibrational energylevel spectrum. The electronic potential energy surfaces and their nonadiabatic coupling arecomputed ab initio. A model Hamiltonian is constructed in a diabatic electronic basis for the nucleardynamical simulations from first principles. Analysis of electronic structure data reveals the relevance of 24 vibrational degrees of freedom in the quantum dynamics of theX-A-B-Ccoupledelectronic states of the radical cation. The complex vibrational energy level spectrum of this coupledelectronic manifold is calculated and assigned. Theoretical results are in excellent accord with theexperimental photoelectron spectroscopy data. The agreements and discrepancies of the theoreticalresults are also recorded and discussed with the mass-analyzed threshold ionization and photoinduced Rydberg ionization and photodissociation spectroscopy results of the X and Celectronic states, respectively. The lifetimes of the excited electronic states of phenylacetyleneradical cation are estimated from the decay of electronic population and are discussed in relation tothe available experimental data.